1. Field of the Invention
This invention relates to an automatic liquid control system for an automatic clothes washing machine. More particularly, the invention relates to an apparatus using ultrasonic sound waves for determining an average clothes load height value and an average deviation value such that an optimum liquid level in the clothes washing machine may be determined.
2. Description of Prior Art
The amount of washing liquid required in an automatic washer for achieving an optimum washing operation is dependent on the clothes load quantity. Accurate clothes load quantity information is necessary therefore, to determine optimum washing liquid volume. Typically, the clothes load quantity is visually determined by the user who then manually selects between several predetermined washing liquid quantities using a manually adjustable liquid level switch.
Various systems have also been developed for automatically determining the clothes load quantity in an automatic washer such that an optimum quantity of washing liquid may be provided. For example, U.S. Pat. No. 5,042,276 discloses a clothes detection means utilizing the inertia of the clothes load for determining the clothes load quantity. A motor is repeatedly energized for rotating an agitator and the clothes load disposed in a wash basket. Between each energization, a pause occurs during which the power supply to the motor is turned off while the speed of the inertial rotation of the agitator is measured to detect the clothes load quantity. The inertial rotation is measured by monitoring the back electromagnetic force created in the motor during the pause. The washing liquid level is then determined from the amount of clothes detected.
In U.S. Pat. No. 4,480,449, an automatic liquid level control is provided which measures the volume of liquid required to be added to a tub to increase the liquid level in the tub by a predetermined increment. The measured amount is compared to a reference amount corresponding to an empty tub. When the measured amount equals the reference amount, the clothes in the washer will be covered and the control terminates introduction of washing liquid into the tub.
The above described methods, however, are relatively costly and complex. It would be advantageous therefore, to develop a system which is relatively less expensive and less complex. Furthermore, it would be advantageous to develop a washing liquid fill system which could accurately determine the clothes load quantity and also account for any significant deviation in clothes load height within the wash basket such as may occur if a pillow or the like is placed in the wash basket.
In the present invention, the inventors contemplate a cloth detection system for an automatic washer utilizing ultrasonic distance measuring system for measuring the quantity of clothes in the wash basket. No prior art teaches or suggests the use of ultrasonic distance measuring systems in an automatic washer, however, ultrasonic distance measuring systems for monitoring the fill level in tanks are well known.
Typically, in these systems, an electroacoustic transducer may be controlled such that it is used alternately as a transmission transducer and as a reception transducer. The electroacoustic transducer is preferably arranged in a container above the highest possible fill level in such a manner that the sonic or ultrasonic pulses transmitted by the transducer strike the surface of the material in the container and the echo pulses reflected at the surface of the material are sent back to the transducer. The excitation of the transducer is by electrical excitation pulses with the frequency of the sonic or ultrasonic wave. The electrical excitation pulses are generated by a pulse generator and applied via a transmission/reception switch to the transducer. The electrical reception signal generated by the transducer in response to the received echo signals are applied via the transmission/reception switch to a processing circuit which determines therefrom the time interval between the instants of transmission of a transmission pulse and the reception of an echo pulse originating from the transmission pulse. This time interval corresponds to the travel time of the ultrasonic wave in the container and is thus an indication of the filling level in the container.
U.S. Pat. Nos. 4,972,386, 4,675,854, and 4,437,497, are all examples of ultrasonic systems for monitoring the fill level within a tank which operate substantially similar to the system described above. None on these patents, however, teach or suggest a system for determining the optimum fill level and then controlling the filling of the tank to the determined optimum fill level. Rather, the systems disclosed in these patents all simply monitor the fill level.
Ultrasonic range finding systems are also well known for use in an ultrasonic range finder camera. U.S. Pat. Nos. 4,439,846, 3,522,764 and 4,199,246 all disclose the use of a sonic range-finder systems in a camera which transmit a burst of sonic energy toward a subject and receives an echo pulse from the subject for determining distance from the transmitter/receiver and the subject. Furthermore, detailed schematic circuit diagrams are shown, in these references, for controlling the ultrasonic transducer utilized within the range finding systems.
From a review of the above described background information, it would therefore appear to be an improvement in the art if a less expensive, more versatile and more accurate system was provided for determining the clothes load quantity in an automatic washer. More particularly, it would be an advancement in the art if a cloth detection system for an automatic washer utilized an ultrasonic distance measuring device for determining the optimum washing liquid level.